Dispersion which contains at least 2 types of particles

Abstract

Aqueous dispersions contain at least two chemically different particle types having a diameter on average of less than 100 μm. The dispersions are resistant to sedimentation and gelling for long periods of time, and can be used for many purposes, such as the polishing of optical surfaces, and in paints and adhesives.

1. An aqueous dispersion which contains at least two chemically different particle types having a diameter on average of less than 100 μm, wherein a first particle type consists of silica, and at least one second particle type is selected from the group consisting of organic resin particles, metal oxide particles other than silica particles, insoluble or poorly soluble ionic particles, and insoluble or poorly soluble mineral particles, wherein the silica particles are present in an amount of at least 50 weight percent based on the total weight of the solids content of the dispersion, which has a viscosity of less than 100 mPa·s measured at 25° C. 
     
     
       2. The aqueous dispersion of  claim 1 , wherein the isoelectric points of two particle types differ by greater than one pH unit. 
     
     
       3. The aqueous dispersion of  claim 1 , wherein at least one second particle is selected from the group consisting of aluminum oxide, boron oxide, zirconium oxide, titanium oxide, zinc oxide, cerium oxide and iron oxide. 
     
     
       4. The aqueous dispersion of  claim 1 , wherein the silica is pyrogenic silica. 
     
     
       5. The aqueous dispersion of  claim 1 , wherein organic additives are present at less than 0.1% by weight. 
     
     
       6. The aqueous dispersion of  claim 1  which has a conductivity of less than 0.1 mS/cm. 
     
     
       7. The aqueous dispersion of  claim 1  which has a conductivity of less than 0.01 mS/cm. 
     
     
       8. The aqueous dispersion of  claim 1  which has a conductivity of less than 0.005 mS/cm. 
     
     
       9. The aqueous dispersion of  claim 1 , wherein organic additives are present in an amount of less than 1% by weight relative to the weight of the aqueous dispersion. 
     
     
       10. The aqueous dispersion of  claim 1 , wherein the conductivity of the aqueous dispersion is less than 1 mS/cm. 
     
     
       11. The aqueous dispersion of  claim 1 , wherein the second particle type is a metal oxide, present in an amount of 0.1 to 5% by weight calculated as the metal, this weight percent relative to the particle solids content of the aqueous dispersion. 
     
     
       12. The aqueous dispersion of  claim 1 , wherein a second particle type consists of aluminum oxide. 
     
     
       13. The aqueous dispersion of  claim 1 , wherein the isoelectric points of two particle types differ by greater than 2.5 pH units. 
     
     
       14. The aqueous dispersion of  claim 1 , wherein the isoelectric points of two particle types differ by greater than four pH units. 
     
     
       15. The aqueous dispersion of  claim 1 , wherein the silica particles have a BET surface area of 100 2 /g to 1000 m 2 /g. 
     
     
       16. The dispersion of  claim 1 , which is free of organic additives.